The present invention relates generally to active metal electrochemical devices. More particularly, this invention relates to Li/air battery cells capable of achieving high energy densities
The large free energy for the reaction of lithium with oxygen has attracted the interest of battery researchers for decades. The theoretical specific energy for lithium/air chemistry far exceeds Li-ion battery chemistry. The high specific energy for metal/air chemistries has long been recognized, as evidenced by the development and commercial success of the Zn/Air battery. However, Li/air chemistry introduces some rather unique challenges.
Lithium is a reactive alkali metal and is incompatible with aqueous electrolytes. Corrosion of the negative electrode due to reaction of the metal anode with water and oxygen in aqueous electrolyte is clearly a much more serious issue for lithium than it is for zinc. The corrosion rate of lithium metal in aqueous electrolytes is on the order of several amps/cm2 for neutral electrolytes and drops to tens of mA/cm2 in highly basic media. Accordingly, with the exception of some early work by Littauer on lithium/water batteries, the historical development of lithium/air batteries has been dominated by the use of aprotic non-aqueous electrolytes.
Essential to the development of aqueous Li/air batteries is the ability to stabilize the lithium anode in the presence of water and oxygen. U.S. Pat. Nos. 7,282,296; 7,282,302; and 7,282,295; and U.S. Patent Application Pub. No.: US 2004/0197641 to Visco et al., disclose protected lithium anodes having protective membranes and protective membrane architectures that are stable in water environments and are capable of discharging into aqueous electrolytes.
The present invention is directed to the furtherer development and enhancement of the overall performance of Li/air battery cells via the chemistry taking place at the cathode.